Making a movie about the film industry isn't meta. Making a movie about making movies is.

Using a footnote to explain another footnote isn't meta. Using a footnote to explain what footnotes are is meta.

Metaphysics, probably the most common use of meta, means that instead of talking about the physics of the real world, you're talking about the physics itself (for example, why should there even be gravity).

2. Ninja in FFXI wasn't meant to be a tank, but it ended up being one in the meta because it's evasion was so high.

Abbreviation of Most Effective Tactic Available. Mostly used when comparing tactics in a game, but can be used in other things as well. It can change over time as new tactics are explored or can change by a change in the rules of a game or availability of new resources. In real life changes to gamerules are usually to make the game more interesting (soccer rules change for offside, usage of time compensation in some courses). In computer games this is done by patching to balance the game or fix bugs.

"Meta" describes a reference made in fiction, where the work reaches outside the narrative and addresses the audience directly or demonstrates awareness of itself as a work of fiction. This is best explained as when a character "breaks the fourth wall", for instance by looking directly at the camera and commenting about the movie or show they are in.

In the TV show Community the character Abed often makes meta references by referring to himself and the other characters as being in a TV show. In response to this, one of them once commented "Abed, it makes the group uncomfortable when you talk about us like we're characters on a show you're watching."

When you create new layers of abstraction between the thing or event, you are becoming more meta.

For example: A footnote that is needed to explain another footnote is meta.

The problem with being meta is that if you add sufficient layers of abstraction or complexity between the original event and the convenient abstractions you create to clarify or explain it, you eventually lose all connection to the original. Generally, you need no more than two or three levels in writing.

Too much meta in your writing leads to meta fog.

In writing, this means your writing sucks.

Man, I need notes to explain the notes to my notes for my thesis!" - "That's very meta. Perhaps you should rewrite it?